A SplitAlgorithm that divides the space of possible keys evenly. Useful
when the keys are approximately uniform random bytes (e.g. hashes). Rows
are raw byte values in the range 00 => FF and are right-padded with
zeros to keep the same memcmp() order. This is the natural algorithm to use
for a byte[] environment and saves space, but is not necessarily the
easiest for readability.

setLastRow

In HBase, the last row is represented by an empty byte array. Set this
value to help the split code understand how to evenly divide the last
region. Note that this last row is inclusive for all rows sharing the
same prefix.